Edge damage distribution at the assemblage level on Middle Stone Age lithics: an image-based GIS approach

Lithic artifacts represent the most abundant cultural remains from Middle Stone Age sites in southern Africa. Of these, pointed forms (under a variety of names), blades, and flakes have long been recognized as the three most abundant general types, and retouch on all three is rare relative to similar forms of equivalent age elsewhere. Here we offer a new technique for documenting concentrations of edge damage on an assemblage level to infer taphonomic processes and to record usewear and retouch. This approach is specifically aimed at patterning on the assemblage scale, rather than on individual artifacts. We use points from a Middle Stone Age assemblage from Pinnacle Point Cave 13B, near Mossel Bay, South Africa, to illustrate the technique. Combining GIS, rose diagrams, and polar statistics, we were able to visually and statistically summarize lithic artifacts for patterns of edge damage. For the points made on quartzite in this assemblage, edge damage was found to be significantly patterned and taphonomic causes of the damage were rejected. The technique also opens avenues for many other quantitative analyses that are either impossible or difficult with current non-visual systems of recording, such as measurements of distance, angle, and area of edge damage.